Determination of P-T conditions of the metamorphic basement by pseudosection modeling in schists of medium grade from the Cumbres Calchaquíes, in the Sierras Pampeanas, NW of Argentina

BELLOS, L.I.; LÓPEZ, J.P; ALTENBERGER, U.; OMRANI, H.; GUNTER, C.

Tucumán

Congreso; XX Congreso Geológico Argentino; 2017

Fac. Cs. Naturales - AGA

In the region of Tafi del Valle, in the NW of Argentina crops out a metamorphic basement of low to medium grade corresponding to the Puncoviscana Formation, assigned to the Late Neoproterozoic / Cambrian. Büttner et al. (2005) proposes for this area a back-arc extensional environment combined with strike slip tectonics along the southwestern Gondwana margin to explain satisfactorily the formation of large sediment basins and the evolution of the region during the Ordovician. However, in the opposite sense, Finch et al (2015) postulate that the El Pichao shear zone, at NW of the studied region, accommodated a significant fraction of convergence velocities driving the orogeny, and that the wide mylonitic shear zones characteristic of the Cambrian- Ordovician deformation of the Sierras Pampeanas result from the convergent movement being taken up by only a few active major shear zones.The aim of this work is to report new thermobarometric data on schists in order to interpret P-T paths for low and medium grade metamorphism of this region using THERIAK-DOMINO software. New values of P-T conditions, close to 4,5 kbar and 550°C are determined from the metamorphic basement reached during the Famatinian Orogenic Cycle (Ordovician-Devonian age).